The invention relates to a method and a device for controlling and regulating a coupling in a motor vehicle transmission in which an electronic control unit determines the behavior of the coupling by means of a regulating circuit.
In the sense of the invention, the coupling is to be understood as a starting clutch. Under this designation fall clutches mounted between an internal combustion engine and an automatic transmission, lock up clutches and also clutches integrated in an automatic transmission which can be used both to start and as selector clutches.
A method for controlling a starting clutch has been disclosed, e.g. in DE 44 09 122 A1. Here the starting control comprises two phases. During a first phase, the input rotational speed of the clutch is brought to a theoretical rotational speed wherein the theoretical rotational speed is established from the driver""s performance standard or the gradient and a driving activity. During the second phase, the difference between the input and the output rotational speeds of the clutch is reduced, according to a theoretical value curve to zero. DE 39 37 976 A1 disclosed a method for regulating the clutch which serves to neutralize vibration. The slip of the clutch is modified according to a revolution uniformity determined from the transmission output. From EP 0 214 989 B2, in turn, the use of a clutch integrated in the automatic transmission as a starting element is known.
Departing from the above described prior art, the problem on which the invention is based is to develop it, with regard to the multiple utilization of a single coupling, in combination with an automatic transmission.
According to the invention, the problem is solved by the present invention. It is advantageous that to control and regulate the coupling exclusively during two operational states, a single regulating circuit is used. The regulated quantity corresponds to the actual value of the differential rotational speed of the coupling. The two operational states correspond to a starting operation, as a first state, and to driving with a variable ratio, as a second state.
During a continuously variable adjustment, a specific regulating circuit, hereinafter designated as a second regulating circuit, determines the behavior of the continuously variable transmission. For this case, i.e. the second state, it is proposed that the first and second regulating circuits be interconnected, via an uncoupling network, wherein the uncoupling network has first and second signal paths. By the uncoupling network, the advantage that the two controllers do not influence each other in their action is thus obtained.
For both operational states, the theoretical value of the differential rotational speed of the coupling is determined from the addition of a theoretical value offset and a ratio-dependent differential rotational speed of the coupling. According to a first characteristic field, the ratio-dependent differential rotational speed is determined for a starting ratio of the continuously variable transmission. The ratio-dependent differential rotational speed for the non-starting ratios is determined via a second characteristic field. Both the first and the second characteristic fields each show a coordination of performance standard of the driver and an output rotational speed of the coupling. The second characteristic fields are configured in a manner such that at a vehicle speed lower than a limiting value, an increased theoretical value of the rotational speed difference results. An active protection against stalling for non-starting ratios is achieved.